1. Field of the Invention
This invention relates to coupling assemblies and, specifically, to microminiature coupling assemblies designed to align and join together the component parts of an optoelectronic package or module. The invention relates particularly to microrobotic devices for very high precision alignment and positioning of the parts of the module.
2. Description of the Prior Art
In the manufacture of optoelectronic modules, such as laser diode packages, it is essential that the light source or laser diode portion and the light receiving optics portion be carefully aligned with each other to optimize light coupling between the two portions. Thus, in the assembly of the parts, a coupling position must be arrived at and maintained with very high precision, typically in the sub-micron range, to ensure optimal light coupling. Various types of alignment apparatuses have been provided to adjust the positions of optoelectronic parts relative to one another so as to assure optimum alignment. However, it has been extremely difficult to maintain this alignment while the parts are joined together to complete the package or module.
One type of package or module may include a base or header portion and a cap portion, each of which is provided with an annular flange defining a planar surface, the planar surfaces of the two flanges being brought together in face-to-face abutting relationship to join the parts together, such as by laser welding. During the welding operation, it is extremely important that the two surfaces that are going to be welded be virtually coplanar, i.e., that they be in contact and parallel within zero to five microns. The surfaces may be held out of parallelism by more than five microns by minute imperfections in the surfaces themselves, by air gaps therebetween and the like. If they are the slightest bit out of parallelism when welded, the welding operation will tend to draw them together to eliminate any gaps or imperfections and thereby destroy the pre-welding alignment which had been achieved. Such minute misalignments can sometimes be corrected, such as by remedial weld applications, but such techniques are time consuming and expensive and, if they fail, the result is a worthless module. This may result in considerable waste, since the components of the package or module themselves can be quite expensive to manufacture.
Minute imperfections and air gaps between the mating surfaces can be eliminated by pressing the surfaces together with sufficient force, but if the parts are not in essentially perfect parallelism before application of the force, it may distort or deform the surfaces, which may itself result in misalignment of the parts or damage thereto.
While a number of systems are known to provide accurate positioning of parts in an X-Y plane, it is sometimes necessary to position parts along the Z axis also. This may occur, for example, in the case of a three-part assembly, wherein two of the parts must be precisely positioned relative to each other along the Z axis and those combined parts must then be precisely positioned relative to a third part along X and Y axes. There is a need for apparatus which can effectively handle and adjust the alignment of parts in all three axes simultaneously prior to joinder of the parts.